Abstract
In general, the students of English Department have the ability to write English well. However, there are still some aspects that must be consideredin writing. Therefore, this study aimed to look at the extent to which students use the sentencestypes in writing an essay. Another aim was to analyze the problems occurred in using the sentencestypes. This research was a descriptive study with research subjects were 22essays of Education 2 Class students in year 2014/2015. Data were collected by analyzing sentences in the essay which were the result of semester exam ofa writing class. Based on the research, there were four sentencestypesin the students’ writing: simple, compound, complex, and compound-complex sentences. Based on the results of the study, it was found that simple sentence was the most sentence types commonly written by the students in writing, by contrast, compound-complex sentencewas the least sentence types written by the student. In addition, there were two problems that occurred to write the sentence types, ie run-on and fragment. Both of these problems were found in all parts of the essay: introduction, main body and conclusion. By doing so, it is expected to the lecturers to pay more attention to the use of different sentence types in students’ writing.